Revert "[irgen] Force emission of objc class refs for non-foreign clang objc classes whose metadata we use."

This reverts commit 8247525. While
correct, it has uncovered several issues in existing code bases that
need to be sorted out before we can land it again.
Fixes rdar://problem/57846390.

Author: DougGregor

lib/IRGen/GenDecl.cpp

@@ -1281,27 +1281,6 @@ void IRGenerator::noteUseOfTypeGlobals(NominalTypeDecl *type,
     }
   }
 
-  // Force emission of ObjC class refs used by type refs.
-  //
-  // Otherwise, autolinking can fail if we try to load the class decl from the
-  // name of the class.
-  if (auto *classDecl = dyn_cast<ClassDecl>(type)) {
-    // The logic behind this predicate is that:
-    //
-    // 1. We need to check if a class decl is foreign to exclude CF classes.
-    //
-    // 2. We want to check that the class decl is objc to exclude c++ classes in
-    //    the future.
-    //
-    // 3. We check that we have a clang node since we want to ensure we have
-    //    something coming from clang, rather than from swift which does not
-    //    have this issue.
-    if (classDecl->hasClangNode() && classDecl->isObjC() && !classDecl->isForeign()) {
-      PrimaryIGM->getAddrOfObjCClassRef(classDecl);
-      return;
-    }
-  }
-
   if (!hasLazyMetadata(type))
     return;
 

test/IRGen/autolink_classlookup_test.swift

@@ -1,9 +1,8 @@
 // RUN: %empty-directory(%t)
 // RUN: cp %s %t/main.swift
-// RUN: %target-clang -c -o %t/ObjCStuff.o -fobjc-arc -I %t -I %S/Inputs/mixed_mode %S/Inputs/mixed_mode/ObjCStuff.m -fmodules
 // RUN: %target-build-swift -whole-module-optimization -emit-module-path %t/UsingObjCStuff.swiftmodule -c -o %t/UsingObjCStuff.o -module-name UsingObjCStuff -I %t -I %S/Inputs/mixed_mode -swift-version 5 -parse-as-library %S/Inputs/mixed_mode/UsingObjCStuff.swift
-// RUN: %target-build-swift -o %t/a.out.v4 -I %t -I %S/Inputs/mixed_mode -module-name main -swift-version 4 %t/main.swift %t/UsingObjCStuff.o %t/ObjCStuff.o
-// RUN: %target-build-swift -o %t/a.out.v5 -I %t -I %S/Inputs/mixed_mode -module-name main -swift-version 5 %t/main.swift %t/UsingObjCStuff.o %t/ObjCStuff.o
+// RUN: %target-build-swift -o %t/a.out.v4 -I %t -I %S/Inputs/mixed_mode -module-name main -swift-version 4 %t/main.swift %t/UsingObjCStuff.o
+// RUN: %target-build-swift -o %t/a.out.v5 -I %t -I %S/Inputs/mixed_mode -module-name main -swift-version 5 %t/main.swift %t/UsingObjCStuff.o
 // RUN: %target-codesign %t/a.out.v4
 // RUN: %target-codesign %t/a.out.v5
 // RUN: %target-run %t/a.out.v4 | %FileCheck %s

test/Inputs/ObjCClasses/framework.module.map

@@ -1,7 +1,7 @@
 // RUN: %empty-directory(%t)
 //
-// RUN: %target-clang -fobjc-arc %S/../Inputs/ObjCClasses/ObjCClasses.m -c -o %t/ObjCClasses.o
-// RUN: %target-build-swift -I %S/../Inputs/ObjCClasses/ %t/ObjCClasses.o %s -o %t/a.out
+// RUN: %target-clang -fobjc-arc %S/Inputs/ObjCClasses/ObjCClasses.m -c -o %t/ObjCClasses.o
+// RUN: %target-build-swift -I %S/Inputs/ObjCClasses/ %t/ObjCClasses.o %s -o %t/a.out
 // RUN: %target-codesign %t/a.out
 // RUN: %target-run %t/a.out